1. Field of the Invention
The present invention relates to an optical disc data recording and reproducing apparatus which optically writes data onto or reads data from an optical disc. More precisely, the invention relates to a driving apparatus which electromagnetically drives an objective lens.
2. Description of Related Art
In a known optical disc apparatus, such as an opto-magnetic disc apparatus, an objective lens is held or supported on a carriage which is movable in a radial direction (i.e., tracking direction) of the optical disc so as to be movable in the tracking direction and the focusing direction through an elastic member. To drive the objective lens in the tracking direction and the focusing direction, tracking and focusing coils are provided on a lens holder, which holds the objective lens, and a magnetic circuit, which constitutes electromagnetic driving circuits together with the tracking and focusing coils, is provided on the carriage. The focusing and tracking coils are supplied with predetermined directions and intensities of electric current to drive the objective lens holder so as to accurately converge the laser beams onto the recording track of the optical disc.
In such an electromagnetic objective lens driving apparatus, the carriage is moved in the radial direction of the optical disc to move the objective lens holder on the carriage. It is necessary to make the carriage and the lens holder as light as possible to quickly access a designated track and to perform precise focusing and tracking operations. However, in the known apparatus, an electrical wiring board (i.e, printed circuit board) on the carriage makes the movable part large and heavy. The printed circuit board is provided to establish an electrical connection of, and power supply to, the focusing coils and tracking coils secured to the objective lens, or electrical connection of, and power supply to, a sensor which is used for the detection of the objective lens holder position. The printed circuit board may also be used for the transmission of output signals of the sensor, etc. The printed circuit board not only limits the degree to which the apparatus can be made small and light, but also is an obstacle in the assembly of the apparatus.
In the known electromagnetic driving apparatus, the sensitivity at a low frequency band must be high to obtain a high dynamic range. However, to realize this, it is necessary that the compliance of the support mechanism be high, so that the objective lens holder can be easily moved by a small driving force. However, a high compliance leads to an accidental or easy downward movement of the objective lens holder by the dead weight thereof. To prevent this, it is necessary to continuously supply an electric current during the driving operation, so that the objective lens holder is stabilized in a floating neutral position ( i.e., servo-position). This, however, increases energy consumption ( i.e. , electric current ) and lowers the driving speed.
The primary object of the present invention is to provide a small and light carriage and objective lens holder without a conventional printed circuit board.
Another object of the present invention is to provide support mechanism of an objective lens holder in which the latter can be magnetically supported even in an inoperative position, so that when an objective lens holder having a high compliance is used, little or no electric current is necessary to float the objective lens holder, unlike the prior art mechanism.